如何通过 TypeScript 中的映射类型删除属性 [英] how to remove properties via mapped type in TypeScript

问题描述

这是代码

class A {
    x = 0;
    y = 0;
    visible = false;
    render() {

    }
}

type RemoveProperties<T> = {
    readonly [P in keyof T]: T[P] extends Function ? T[P] : never//;
};


var a = new A() as RemoveProperties<A>
a.visible // never
a.render() // ok!

我想通过 RemoveProperties 删除visible/x/y"属性，但我只能用 never 替换它

I want to remove " visible / x / y " properties via RemoveProperties ,but I can only replace it with never

推荐答案

您可以使用与 Omit 类型使用:

You can use the same trick as the Omit type uses:

// We take the keys of P and if T[P] is a Function we type P as P (the string literal type for the key), otherwise we type it as never. 
// Then we index by keyof T, never will be removed from the union of types, leaving just the property keys that were not typed as never
type JustMethodKeys<T> = ({[P in keyof T]: T[P] extends Function ? P : never })[keyof T];  
type JustMethods<T> = Pick<T, JustMethodKeys<T>>; 

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